This invention relates to a tank assembly and more particularly to a mechanically sealed joint used to connect a filler pipe to a fuel storage tank.
Automotive fuel tanks are commonly mounted such that they are concealed from above by the vehicle's body. Therefore, a filler pipe is generally routed from the surface of the body to the tank itself. The filler pipe begins as a separate component that is attached to the tank at the pipe's filler neck thereby forming a fuel tank assembly. The filler pipe may be one piece or an assembly of components with the filler neck attached to the fuel tank and the remainder of the filler pipe assembly attached to the filler neck.
Also included in a fuel tank assembly is generally a vent pipe that conveys air from the tank during refueling. The vent pipe may be integral with the fill pipe or may be separately attached to the fuel tank in a manner similar to that by which the filler pipe is attached. A fuel tight seal must be provided at the joint between the pipes and the fuel tank to avoid leaks.
The predominant method of providing a seal at the filler neck joint is to extend the neck of the filler pipe through an opening in the fuel tank and solder the adjoining material of the two components to form an assembly. Generally a lead-tin material is used to solder the joint. The filler neck may be provided with a lead-tin coating or the like to obtain a secure solder joint and provide corrosion resistance.
With soldered construction, a clean metal surface on the tank and filler neck must be provided at the joint. The tank generally has a corrosion resistent coating on the base metal that may have to be removed in the area to be soldered. A problem with removing the coating is that the corrosion resistance aspect is defeated by exposing the base metal. Therefore a reapplication of additional corrosive resistant material may be required to obtain an acceptable corrosion free life expectancy from the assembly.
When an alcohol such as methanol is used as a fuel the typical lead-tin solder may be incompatible with the fuel and cannot be used in the fuel tank assembly. In such situations a solder and filler neck comprised of alternative materials may be required adding expense to the tank and filler pipe assembly when using a solder joint. Alternative, more expensive materials may also be used when preferable to reduce the use of lead in soldered joint construction.
Another method of connecting a filler pipe to a fuel tank involves the use of a resilient grommet. In this type of assembly the grommet is inserted into an opening in the fuel tank and then the filler neck is clamped or fastened to the grommet. The resiliency of the grommet allows it to deform and may permit movement of the filler pipe relative to the tank.
The above described assembly techniques provide advantages that are desirable. A soldered joint provides a leak tight seal with a high resistance to separation. A grommet joint provides a leak tight seal with resiliency and ease of assembly. Both assemblies have been used successfully in automotive applications. However, there remains a need for a durable, easily assembled filler neck joint that performs with a wide range of vehicle fuels and preserves the corrosion resistive integrity of the component parts.